for a natural apirated engine like one on your car, I would suggest supercharger... I am no expert but Ive heard tremendous gains on HP. but yes they are expensive. so it depends on your budget. how much were you thnking of spend and do you want your mod to e exclusively on performance? I do think that there should be a room for a improvement on your engine... i dont know how much though. then there are transmission and tires to think of... so yea, it can be a bit of a dough but I am pretty sure it can be done.
hope you get the best results!